"Oftentimes, the victims are people who are brought here illegally or are here and their visa expired," Rubio said. "And they're terrified about cooperating with prosecutors against their pimps or the organized crime syndicate because they believe they're going to be deported."

But that could be a pathway to a perverse type of amnesty. And that's a problem in a nation where Congress has been unable to comprehensively address illegal immigration — a central issue in the Republican race for president where the word "amnesty" is a slur.

"It's been a factor. Some people have talked about it. The concern is not the victims," Rubio said. "The concern is that someone would exploit this and use it as a loophole to somehow game the system. You're always concerned about somebody gaming the system. This is a law that's designed to help victims of trafficking and exploitation."

Rubio made his remarks during a press conference held at Kristi House, a Miami home for abuse victims. Rubio said he ultimately expects the legislation will pass Congress by year's end with "strong bipartisan support" after lawmakers figure out how to prevent people from abusing the law designed to stop abuse.

The federal legislation is partly a reauthorization of an existing law, set to expire, that aims to give federal prosecutors and aid workers the chance to stop human trafficking across state lines.

Sometimes, victims are treated like criminals, said state Rep. Jeanette Nuñez, R-Miami. She and fellow Miami Republican Rep. Erik Fresen are sponsoring state legislation that would increase penalties on wrongdoers and would require police to take suspected victims to a "safe house" instead of a juvenile-detention facility.

"These child victims of prostitution are being treated like prostitutes," Nuñez said. "This bill is seeking to address the victim — and make them be just that: victims. Right now, they're treated as criminals. They're processed through the juvenile assessment center."

The number of sex-trafficking victims is unknown. Some estimate the number to be as high as 300,000. Not all are girls or women. Not all are involved in the sex trade. Not all are here illegally. But most are, social service advocates say.

It's a particularly thorny problem in a state like Florida and a county like Miami-Dade, which has a large immigrant population where undocumented immigrants can thrive — or be exploited.

"You hear about this and you think: 'yeah that's something that happens halfway around the world' " Rubio said. "It's happening right here in your hometown."